"He's made this a contest not so much about voting yes or no on the constitutional reforms, he's saying that anyone who votes yes will be voting in favour of President Chavez and those who vote no are voting against him," she said.

"Chavez is a very popular president still and he is counting on his own personal appeal to get the vote out in his favour."

Proposals to cut daily work hours from eight to six, and to reinforce social welfare programmes have been particularly welcomed by the country's poor.

"Chavez has become a father for us," Xiomi Diaz, a farmer, said at the rally. "He's a father of the poor."

However, more than 100,000 people turned out to march against the plan on Thursday, concerned about the fact that term limits for the president would be scrapped and his mandate would be increased from six years to seven.

"We'll have one person who'll rule the country as he wants, without any restrictions, without any controls, without any limitations," Adolfo Taylhardat, a lawyer, told Al Jazeera.

Chavez said at Friday's rally: "If God gives me life and help, I will be at the head of the government until 2050."

Fundamental rights

Human Rights Watch also said that the proposed changes threatened fundamental rights.

"These amendments would enable President Chavez to suspend basic rights indefinitely by maintaining a perpetual state of emergency," Jose Miguel Vivanco of the New York-based group said in a statement on Thursday.

More than 100,000 opponents of the changes urged people to vote "no" [AFP]

The government would be allowed to censor the media in times of "emergency", as well as take over the central bank and expropriate property in the name of "economic socialism".

Opponents have questioned the national electoral council's impartiality ahead of the poll, especially after Chavez named Jorge Rodriguez, its former chief, as his vice-president in January.

About 100 electoral observers from 39 countries in Latin America, Europe and the US are on hand, plus hundreds of Venezuelan observers, according to the council.

In Washington, Sean McCormack, US state department spokesman, said that the United States hoped the referendum would be "a free and fair contest in which the will and desire of the Venezuelan people is reflected".

Chavez on Friday threatened to cut off oil supplies to the US, who he accuses of backing a failed coup attempt against him in 2002, if they interfered in the poll.

"There will not be a single drop of oil for the United States," he said. "And if they want to come and take our oil they will face 100 years of war in Venezuela."